The recovery of a gaseous component from a gas mixture in a process and the use of that recovered component in another process is a common operation in the process industries. For example, carbon dioxide is a common constituent of synthesis gas, and carbon dioxide often must be removed before the synthesis gas is introduced into reaction systems for the production of methanol, ammonia, dimethyl ether, and synthetic hydrocarbons. In order to improve the overall carbon utilization of such processes, it is often desirable to recycle carbon dioxide, or in some cases to import carbon dioxide, to be utilized in the feed to one of the upstream reaction systems. In other cases, carbon dioxide can be removed from the synthesis gas and exported for use elsewhere.
In gas separation processes to recover a component or components from a multicomponent feed gas mixture, the recovered components typically are obtained at a pressure below the feed gas pressure. In a distillation process, for example, the product streams are obtained at pressures which are slightly lower than the feed gas pressure due to pressure drop in the distillation column. In a membrane separation process, permeate product gas is recovered at a pressure significantly lower than the feed gas pressure and non-permeate product gas is recovered at pressures which are slightly lower than the feed gas pressure due to pressure drop in the membrane module. In a pressure swing adsorption process, the more strongly adsorbed components are recovered by depressurization to a pressure below the feed pressure and the less strongly adsorbed components are recovered at pressures which are slightly lower than the feed gas pressure due to pressure drop in the adsorbent bed.
A gaseous product recovered from a feed gas mixture in a separation process and used in another process may be required at a pressure higher than the separation process operating pressure. In this case, the gaseous product must be compressed before use in the other process. In order to reduce or eliminate the compression required in this situation, it would be desirable to obtain the gaseous product from the separation process at a pressure above the feed gas pressure and preferably at the pressure required in the other process. Embodiments of the invention described below address this need by providing a gas separation process that can generate a product gas mixture at pressures above the feed gas pressure.